CN114759562B - Common coupling point harmonic suppression method based on grid-connected inverter - Google Patents
Common coupling point harmonic suppression method based on grid-connected inverter Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/01—Arrangements for reducing harmonics or ripples
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
- H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
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- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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Abstract
A public coupling point harmonic suppression method based on a grid-connected inverter solves the problem that the existing fixed parameter virtual impedance is not enough in adaptability to a dynamic harmonic environment of a power grid, and belongs to the field of grid-connected inverter control and harmonic suppression. The invention comprises the following steps: collecting power grid current and PCC voltage, and obtaining total harmonic power of the power grid in the current period; subtracting the total harmonic power of the power grid in the current period from the total harmonic power of the power grid in the previous period to obtain a total harmonic power difference value of the power grid, and subtracting the virtual impedance parameter in the current period from the virtual impedance parameter in the previous period to obtain a virtual resistance difference value; the virtual impedance parameter can be a virtual resistance value, a virtual capacitance value or a virtual inductance value; judging the magnitude of the power grid total harmonic power difference value and the magnitude of the virtual resistance difference value, and combining the adjustment factorsBCalculating the value of the virtual impedance parameter of the next period; and determining virtual impedance according to the virtual impedance parameter of the next period, and performing harmonic suppression of the point of common coupling according to the virtual impedance.
Description
Technical Field
The invention provides a public coupling point harmonic suppression method based on self-adaptive virtual impedance, and belongs to the field of grid-connected inverter control and harmonic suppression.
Background
The development of renewable energy sources and the establishment of a sustainable energy system have become necessary requirements for sustainable and high-quality development of the economic society of China. The grid-connected inverter is used as a grid-connected interface of the renewable energy power generation unit, is connected to a power grid through a Point of Common Coupling (PCC), performs power exchange with the power grid, and is an essential link for renewable energy power generation. With the development of industry and the improvement of the living standard of people, the types and the number of power electronic devices and nonlinear loads accessed by a power grid are more and more, so that the PCC voltage harmonic problem is more serious. Harmonic waves not only reduce the quality of electric energy of a power grid, but also damage electric equipment, and even threaten the safety and economic benefits of users. To solve the harmonic problem, a dedicated compensation device such as an Active Power Filter (APF) is usually used to compensate the power grid harmonic. The APF has good harmonic suppression effect, but the manufacturing cost is expensive, and the economic cost is additionally increased. The grid-connected inverter and the APF have similar topological structures, benefit from the flexibility and intelligence of the control of the power electronic device, and can add a harmonic wave treatment function except for transmitting energy to a power grid to the grid-connected inverter by changing the control strategy of the traditional grid-connected inverter, thereby avoiding the cost investment of a special compensation device, improving the utilization rate of the grid-connected inverter, and realizing the win-win of the electric energy quality treatment and the economic benefit.
Most of the existing PCC voltage harmonic suppression methods based on grid-connected inverters need to collect current at a nonlinear load, but the load access position in an actual power grid cannot be determined, and load harmonic source current information is difficult to collect. The virtual impedance control method can inhibit the harmonic distortion of the PCC voltage by only acquiring the PCC voltage, and is suitable for improving the quality of the actual PCC power. The existing virtual impedance control method mainly comprises a resistance type and a resistance-inductance type, the harmonic suppression effect of the two virtual impedances is limited by fixed impedance parameters, and the harmonic suppression effect of the grid-connected inverter is reduced because the parameters cannot be dynamically adjusted according to the change of the actual power grid harmonic power. And the resistance type virtual impedance control method has poor harmonic suppression stability, the resistance type virtual impedance control method has insufficient high-frequency harmonic suppression capability, and a novel virtual impedance control method with both harmonic suppression stability and broadband harmonic suppression range is lacked.
Disclosure of Invention
The invention provides a public coupling point harmonic suppression method based on a grid-connected inverter, aiming at the problem that the existing fixed parameter virtual impedance is not enough in adaptability to a dynamic harmonic environment of a power grid.
The invention discloses a method for suppressing a harmonic wave at a point of common coupling based on a grid-connected inverter, which comprises the following steps:
s1, collecting the current of the power gridi g (n) And PCC voltagev pcc (n) At grid currenti g (n) Extracting harmonic component of current in PCC voltagev pcc (n) Extracting voltage harmonic component, and obtaining total harmonic power of the power grid in the current period according to the voltage harmonic component and the power grid current harmonic componentP t (n)，nRepresenting the current cycle;
s2, converting the total harmonic power of the power grid in the current periodP t (n) The total harmonic power of the power grid in the last periodP t (n-1) subtracting to obtain the total harmonic power difference value delta of the power gridP t (n) The virtual impedance parameter of the current cycleK v (n) And the virtual impedance parameter of the previous periodK v (n-1) subtracting to obtain a virtual resistance difference value ΔK v (n) (ii) a Virtual impedance parameterK v Can be a dummy resistorR v Virtual capacitorC v Or virtual inductanceL v ；
S3, determining the virtual impedance parameter of the next periodK v (n+1)：
If ΔP t (n) Equals to 0, let the next cycle virtual impedance parameterK v (n+1) is equal to the virtual impedance parameter of the current cycleK v (n) Go to S4;
if ΔP t (n) Less than 0, judging ΔK v (n) If it is greater than 0, making the virtual impedance parameter of next periodK v (n+1) is equal to the current period virtual impedance parameterK v (n) And regulatory factorBGo to S4; if not, the virtual impedance parameter of the next period is madeK v (n+1) is equal to the current period virtual impedance parameterK v (n) And regulatory factorBAnd (3) going to S4;
if ΔP t (n) If it is greater than 0, determine ΔK v (n) If it is greater than 0, making the virtual impedance parameter of next periodK v (n+1) is equal to the virtual impedance parameter of the current cycleK v (n) And regulatory factorBAnd (3) going to S4; if not, the virtual impedance parameter of the next period is madeK v (n+1) is equal to the virtual impedance parameter of the current cycleK v (n) And regulatory factorBGo to S4;
regulating factorB：
Wherein the content of the first and second substances,drepresents an adaptive coefficient;
s4, according to the virtual impedance parameter of the next periodK v (n+1) determining the virtual impedanceZ v According to virtual impedanceZ v And carrying out common coupling point harmonic suppression.
Preferably, in S4, the virtual impedanceZ v Comprises the following steps:
wherein the content of the first and second substances,sis the laplacian operator.
Preferably, the virtual impedance parameterK v Is a virtual resistanceR v Said S4 includes:
s41, determining virtual impedanceZ v ；
S42 sampling PCC voltagev pcc And grid-connected current of grid-connected inverteri 2 Extracting PCC voltagev pcc Fundamental component of (2)v base And harmonic componentsv harm (ii) a Fundamental componentv base Obtaining the synchronous angle of the power grid through a phase-locked loopθ；
S43, synchronizing angles by using power gridθFor fundamental componentv base D-axis component obtained after park transformationv d And q-axis componentv q Sending the reference value of power current to a calculation module, and calculating the power according to the active instructionP * And reactive command powerQ * D-axis component of power current reference value is obtained through calculationi brefd And q-axis component of power current reference valuei brefq ；
S44, according to harmonic componentv harm And a virtual impedanceZ v Obtaining a reference value of the impedance remodeling currenti href ：
Synchronizing angles using a power gridθReshaping impedance to a current reference valuei href Performing park transformation to obtain d-axis component of impedance remodeling current reference valuei hrefd And impedance reshape current reference q-axis componenti hrefq ；
S45, reshaping the impedance into a d-axis component of the current reference valuei hrefd And d-axis component of power current reference valuei brefd Adding to obtain a grid-connected current d-axis reference valuei dref The impedance is reshaped to the q-axis component of the current reference valuei hrefq And q-axis component of power current reference valuei brefq Adding to obtain a grid-connected current q-axis reference valuei qref ；
S46, merging the grid currenti 2 Performing park transformation to obtain a grid-connected current d-axis componenti d And grid-connected current q-axis componenti q And respectively connected with the grid-connected current d-axis reference valuei dref And grid-connected current q-axis reference valuei qref Comparing, and sending the error amount to a current tracker;
s47, obtaining three-phase modulation quantity after current decoupling of output of the current trackermFor three-phase modulationmAnd performing PWM modulation, generating a driving signal for controlling a switching tube of the grid-connected inverter, and sending the driving signal to the grid-connected inverter.
Preferably, the dummy inductanceL v And selecting according to the low harmonic content of the actual PCC voltage harmonic.
Preferably, the dummy capacitorC v And selecting according to the actual PCC voltage harmonic higher harmonic content.
Preferably, S1 includes:
s11, sampling PCC voltagev pcc (n) And the current of the power gridi g (n)；
S12, extracting the product to be inhibitedhsub-PCC voltage harmonic componentv pcch (n) Andhsub-grid current harmonic componenti h (n) CalculatinghSub-grid harmonic powerP h (n) And total harmonic power of power gridP t (n)：
In the formula (I), the compound is shown in the specification,hrepresenting the frequency of the desired suppression voltage harmonic,Nrepresenting the maximum frequency of the desired suppressed voltage harmonics,
representing the PCC voltagehSub-harmonic componentv pcch (n) In the form of a plurality of numbers of (a),
representing grid currenthSub-harmonic componenti h (n) In the form of a plurality of such compounds,
representing the real component of the product.
The method has the advantages that by improving the control structure of the grid-connected inverter, under the condition of ensuring the harmonic suppression stability of the grid-connected inverter, the virtual impedance parameter value is adjusted by self-adapting the harmonic power of the power grid, the grid-connected inverter can well suppress low-frequency voltage harmonic waves and high-frequency voltage harmonic waves, the wide-frequency-domain harmonic suppression capability and the complex harmonic environment adaptability of the grid-connected inverter are effectively enhanced, and the electric energy quality of a public coupling point is further improved.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a schematic diagram of the principle of grid-tied inverter based PCC harmonic suppression of the present invention; wherein the content of the first and second substances,u dc which represents the voltage on the direct-current side,L f1 representing the grid-connected inverter side filter inductance,C f which represents the filter capacitance, is,L f2 represents the filter inductance on the side of the power grid,i 1 representing the output current of the grid-connected inverter,i 2 which represents the current of the grid-connection,i a representsaThe phase-to-grid current is,i b representsbThe phase-to-grid current is,i c representscThe phase-to-grid current is,v pcca representing points of common couplingaThe phase voltages are set to be equal to each other,v pccb representing points of common couplingbThe phase voltages are set to be equal to each other,v pccc representing points of common couplingcThe phase voltages are set to be equal to each other,Z g representing the impedance of the power grid,v ga representsaThe phase of the grid voltage is set to be,v gb representsbThe phase of the grid voltage is set to be,v gc representscThe phase of the grid voltage is set to be,i g representing the grid current, ISOGI representing the ISOGI harmonic extraction algorithm,v harm representing the PCC voltagev pcc The harmonic component of (a) is,v base representing the PCC voltagev pcc RIC represents the RIC virtual impedance block, PLL represents the phase locked loop,θrepresenting the angle of synchronization of the grid,i href representing the impedance reshaped current reference value, abc/dq representing the park transformation, dq/abc representing the inverse park transformation,i hrefd representing the d-axis component of the impedance-reshaped current reference,i hrefq representing impedance-reshaped current parameterBy reference to the q-axis component of the value,v based representsv base The d-axis component of (a) is,v baseq representsv base Q-axis component of (a), PQ represents the power current reference value calculation module,i brefd representing the d-axis component of the power current reference,i brefq representing the q-axis component of the power current reference value,i dref representing the grid-tied current d-axis reference value,i qref representing the grid-connected current q-axis reference value,i d representing the d-axis component of the grid-tied current,i q representing the q-axis component of the grid-connected current,ω 0 representing fundamental angular frequency, PIMQR representing a PIMQR current tracker, Deltai d Representing d-axis current tracker output, Δi q Representing the q-axis current tracker output value,m d represents the amount of modulation on the d-axis,m q represents the amount of modulation on the q-axis,m a representsaThe amount of phase modulation is controlled,m b representbThe amount of the phase modulation is controlled,m c representscThe phase modulation amount, PWM stands for PWM modulation block,S a1 representsaIn contrast to the tube drive signal,S a2 representsaThe tube drive signals are phase-out of phase,S b1 representbIn contrast to the tube drive signal,S b2 representsbThe tube drive signals are phase-out of phase,S c1 representscIn contrast to the tube drive signal,S c2 representscThe tube drive signals are phased out.
FIG. 3 is a low frequency equivalent circuit diagram of a grid-connected system;
FIG. 4 is a high frequency equivalent circuit diagram of a grid-connected system;
FIG. 5 is a graph of PCC voltage prior to use of the method of the present embodiment;
FIG. 6 is a graph of a Fourier analysis of a PCC voltage prior to use in the method of the present embodiment;
FIG. 7 is a graph of PCC voltage after the method of the present embodiment;
fig. 8 is a graph of a fourier analysis of PCC voltage after the method of the present embodiment is used.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.
The method for suppressing the harmonic wave of the common coupling point based on the grid-connected inverter comprises the following steps of;
and adjusting the virtual impedance parameter values, observing the change direction of the total power of the harmonic waves of the power grid, and determining the adjustment direction of the virtual impedance parameter in the next working period so as to adjust the parameter towards the direction of reducing the total power of the total harmonic waves of the power grid.
The step 1 specifically comprises the following steps:
step 11, sampling the PCC voltagev pcc (n) And the current of the power gridi g (n)；
Step 12, extracting the product to be inhibitedhsub-PCC voltage harmonicsComponent(s) ofv harm (n) Andhsub-grid current harmonic componenti h (n) CalculatinghSub-grid harmonic powerP h (n) And total harmonic power of power gridP t (n)：
In the formula (I), the compound is shown in the specification,hrepresenting the frequency of the desired suppression voltage harmonic,Nrepresenting the maximum frequency of the desired suppressed voltage harmonics,
representing the PCC voltagehSub-harmonic componentv harm (n) In the form of a plurality of numbers of (a),
representing grid currenthSub-harmonic componenti h (n) In the form of a plurality of such compounds,
represents the real component of the product and,nrepresenting the current cycle.
Step 2, the total harmonic power of the power grid in the current period is measuredP t (n) The total harmonic power of the power grid in the last periodP t (n-1) subtracting to obtain the total harmonic power difference value delta of the power gridP t (n) The virtual impedance parameter of the current cycleK v (n) And the virtual impedance parameter of the previous periodK v (n-1) subtracting to obtain a virtual resistance difference value ΔK v (n) (ii) a Virtual impedance parameterK v Can be a dummy resistorR v Virtual capacitorC v Or virtual inductanceL v ；
Step 3, determining the virtual impedance parameter of the next periodK v (n+1)：
If ΔP t (n) Equals to 0, let the next period virtual impedance parameterK v (n+1) is equal to the virtual impedance parameter of the current cycleK v (n) Turning to step 4;
if ΔP t (n) Less than 0, judging ΔK v (n) If it is greater than 0, making the virtual impedance parameter of next periodK v (n+1) is equal to the current period virtual impedance parameterK v (n) And regulatory factorBIf so, go to step 4; if not, the virtual impedance parameter of the next period is madeK v (n+1) is equal to the virtual impedance parameter of the current cycleK v (n) And regulatory factorBAnd (4) turning to the step 4;
if ΔP t (n) If it is greater than 0, determine ΔK v (n) If the impedance is larger than 0, the virtual impedance parameter of the next period is judged to be larger than 0K v (n+1) is equal to the current period virtual impedance parameterK v (n) And regulatory factorBAnd (4) turning to the step 4; if not, making the virtual impedance parameter of the next period equal to the virtual impedance parameter of the current periodK v (n) And regulatory factorBIf so, go to step 4;
regulating factorB：
Wherein the content of the first and second substances,drepresents an adaptive coefficient;
virtual impedance adaptive adjustment factorBThe calculation formula comprises the change rate of the total harmonic power, and the adjustment factor can automatically adjust the size to track the change condition of the adaptive power value. When the distance from the optimal absorbed power point is far, the adjustment factor is large, and the searching speed is increased; when the point is close to the optimal absorbed power point, the adjustment factor is small, and the search accuracy is improved; when the optimal absorbed power point is reached, a 0 regulating factor is adopted to stabilize the system at the optimal absorbed power point and prevent oscillation near the maximum power point. The grid-connected inverter can quickly find out the optimal virtual impedance parameter under the harmonic wave of the broadband power grid, and the fixed parameter acquisition of the virtual impedance is broken throughThe method has the advantages that the method is limited in harmonic suppression capability of the grid-connected inverter, adaptability of the grid-connected inverter to complex harmonic environments is improved, and the effect of the grid-connected inverter on voltage harmonic suppression of a point of common coupling is enhanced.
Step 4, according to the virtual impedance parameter of the next periodK v (n+1) determining the virtual impedanceZ v According to a virtual impedanceZ v And carrying out common coupling point harmonic suppression.
According to the embodiment, the power grid harmonic power information is introduced into the virtual impedance adjusting factor, the optimal virtual impedance parameter value under the broadband domain harmonic can be calculated on line by tracking the power grid harmonic power change in a self-adaptive manner, the limitation of the fixed parameter virtual impedance on the harmonic suppression capability of the grid-connected inverter is broken through, and the broadband domain harmonic suppression capability and the dynamic harmonic environment adaptability of the grid-connected inverter are enhanced. The method comprises two parts of power grid harmonic power calculation and virtual impedance parameter value updating, the impedance adjusting factor is updated in a self-adaptive mode according to the change direction of the power grid harmonic power, the optimal virtual impedance parameter under the broadband domain harmonic can be found out quickly and accurately, the problem that the limitation of the fixed virtual impedance parameter on the harmonic suppression capability of the grid-connected inverter is solved, and the broadband domain harmonic suppression capability and the complex harmonic environment adaptive capability of the grid-connected inverter are improved.
In a preferred embodiment, the virtual impedance parameterK v Is a virtual resistanceR v Determining the virtual resistance of the next cycle, as shown in FIG. 1R v Step 4 of the present embodiment includes:
step 41, according to the virtual resistanceR v Virtual inductorL v Virtual capacitorC v Determining a virtual impedanceZ v ：
Wherein the content of the first and second substances,sis the laplacian operator.
Virtual inductor in this embodimentL v Can be based on the low harmonic content of the practical PCC voltage harmonicMake a selection, the virtual capacitanceC v Can be selected according to the actual PCC voltage harmonic higher harmonic content, virtual resistanceR v The values of the low-order harmonic and the high-order harmonic need to be considered seriously because the suppression effects of the low-order harmonic and the high-order harmonic are simultaneously influenced, and the method can be obtained by using the methods from the step 1 to the step 3.
Step 42, sampling the PCC voltagev pcc And grid-connected current of grid-connected inverteri 2 Extracting PCC voltage by using ISOGI harmonic extraction algorithmv pcc Fundamental component ofv base And harmonic componentsv harm (ii) a Fundamental componentv base Obtaining the synchronous angle of the power grid through a phase-locked loopθ，θUsed for carrying out park coordinate transformation;
the ISOGI harmonic extraction algorithm has the characteristics of high harmonic extraction speed and accurate extraction, and the expression is as follows:
kin order to be a damping coefficient of the damping,ωfor the frequency of the voltage to be extracted, by controllingωThe fundamental component and the harmonic component of the particular sub-PCC voltage to be suppressed can be extracted,G ISOGI (s) represents the transfer function of the ISOGI harmonic extraction algorithm.
Step 43, synchronizing angles by using the power gridθFor fundamental componentv base D-axis component obtained after park transformationv d And q-axis componentv q Sending the reference value of power current to a calculation module, and calculating the power according to the active instructionP * And reactive command powerQ * D-axis component of power current reference value is obtained through calculationi brefd And q-axis component of power current reference valuei brefq ；
Step 44, harmonic componentv harm Running into RIC virtualizationAn impedance module for obtaining an impedance-reconstructed current reference valuei href ：
Synchronizing angles using a power gridθReshaping impedance to a current reference valuei href Performing park transformation to obtain d-axis component of impedance remodeling current reference valuei hrefd And impedance reshape current reference q-axis componenti hrefq ：
The RIC virtual impedance module displays a resistance series inductance characteristic under low-order harmonic waves and a resistance series capacitance characteristic under high-order harmonic waves, can effectively remold the impedance frequency characteristic of the grid-connected inverter through reasonable design parameters, and provides a low impedance path for the low-order harmonic waves and the high-order harmonic waves.
FIG. 3 is a low-frequency equivalent circuit diagram of a grid-connected system based on RIC virtual impedance, and a grid-connected inverter can be equivalent to a current sourcei inv Parallel output impedanceZ o 。
When the inverter uses the RIC virtual impedance control method, the RIC virtual impedance is displayed in a state that the virtual resistor is connected with the virtual inductor in series under low frequency, and the virtual capacitor does not play a role. By reasonably designing the virtual resistorR v And a virtual inductorL v The value of the voltage can remold the low-frequency impedance characteristic of the grid-connected inverter and give a stable low-impedance path to the PCC low-order harmonic, so that the low-order harmonic content in the PCC voltage is reduced.
Fig. 4 is a high-frequency equivalent circuit diagram of a grid-connected system based on RIC virtual impedance. When the inverter uses the RIC virtual impedance control method, the RIC virtual impedance is displayed in a state that a virtual resistor is connected with a virtual capacitor in series at high frequency, and the virtual inductor does not play a role. By reasonably designing the virtual resistorR v And a virtual capacitorC v Can reshape the high-frequency impedance of the grid-connected inverterThe characteristic is that a stable low impedance path is provided for the PCC higher harmonic wave, thereby reducing the higher harmonic wave content in the PCC voltage.
Due to the specific frequency characteristics of the RIC virtual impedance, the RIC virtual impedance has good and stable inhibition effect on the low-order voltage harmonic and the high-order harmonic of the PCC.
Step 45, reshaping the impedance to obtain a d-axis component of the current reference valuei hrefd And d-axis component of power current reference valuei brefd Adding to obtain a grid-connected current d-axis reference valuei dref The impedance is reshaped to the q-axis component of the current reference valuei hrefq And q-axis component of power current reference valuei brefq Adding to obtain a grid-connected current q-axis reference valuei qref ；
Grid-connected current d-axis reference valuei dref And grid-connected current q-axis reference valuei qref Both are mixed signals comprising a dc signal and an ac signal. If it is necessary to suppress multiple frequency harmonics simultaneously, both of them are mixed signals including a dc signal and ac signals of multiple frequencies, so that a current tracker capable of tracking the dc signal and the ac signals of multiple frequencies simultaneously is used for reference current tracking.
Step 46, grid connection currenti 2 Performing park transformation to obtain a grid-connected current d-axis componenti d And grid-connected current q-axis componenti q And respectively connected with the grid-connected current d-axis reference valuei dref And grid-connected current q-axis reference valuei qref Comparing, and sending the error amount into a PIMQR current tracker;
the PIMQR current tracker can track a direct current signal and alternating current signals with various frequencies at the same time, and the expression is as follows:
in the formulak p Is a coefficient of proportionality that is,k i in order to be the integral coefficient of the light,ω 0 is the angular frequency of the fundamental wave,ω c in order to cut the frequency of the wave,k r is harmonic toThe vibration coefficient of the vibration generator is as follows,kthe highest order of voltage harmonics that are desired to be suppressed,
representing the transfer function of the PIMQR current tracker.
Step 47, obtaining a three-phase modulation value after current decoupling of the output of the current trackermFor three-phase modulationmPerforming PWM modulation, generating a driving signal for controlling a switching tube of the grid-connected inverter, and sending the driving signal to the grid-connected inverter:
whereinm d Represents the amount of modulation on the d-axis,m q representing the q-axis modulation amount. Deltai d Representing d-axis current tracker output, Δi q Representing the q-axis current tracker output value.i d Representing the d-axis component of the grid-tied current,i q representing the grid-connected current q-axis component.ω 0 Representing the angular frequency of the fundamental wave of the voltage,L f1 representing the filter inductance on the inverter side,L f2 representing the grid side filter inductance.
Modulating d-axis by an amountm d And q-axis modulation amountm q Obtaining three-phase modulation quantity through inverse Pack transformationm a 、m b 、m c Sending the three-phase modulation quantity into a PWM (pulse-Width modulation) module to generate 6 paths of driving signals for controlling the on and off of a switching tubeS a1 、S a2 、S b1 、S b2 、S c1 AndS c2 。
when current is connected to the gridi 2 Tracking to a current reference valuei ref In the process, besides the function of transmitting power according to a power instruction, the grid-connected inverter can also present a low impedance state at low frequency and high frequency by remolding the frequency characteristic of self output impedance, stably inhibit PCC low-frequency voltage harmonic waves and high-frequency voltage harmonic waves, and further improve the PCC electric energy quality.
A simulation model is built in PLECS simulation software, 5-order alternating current voltage source with the effective value of 11V is used for simulating power grid background harmonic, an uncontrolled rectifier bridge load is used for simulating a nonlinear load, the power grid load is a 15 omega resistance load, the effectiveness of the method provided by the embodiment is verified,
fig. 5 shows that the PCC voltage is distorted severely under the influence of grid background harmonics and nonlinear loads, when the total harmonic distortion rate is 20.51%.
Fig. 6 shows that the PCC voltage harmonics contain multiple frequency harmonics of 5 th, 7 th, 11 th, 13 th, etc.
Fig. 7 shows that the PCC voltage distortion is greatly suppressed after the method of the present embodiment is used, and the total harmonic distortion rate is 9.66%.
Fig. 8 shows that the harmonic content of the PCC voltage at various frequencies is greatly reduced after the method of the present embodiment is used.
The simulation results of fig. 7 and 8 verify the effectiveness and practicality of the method of the present embodiment.
According to the embodiment, the PCC voltage and the grid-connected current output by the grid-connected inverter are collected, the PCC voltage harmonic information is introduced into the reference values of the d-axis component and the q-axis component of the grid-connected current through the RIC virtual impedance, the parallel RIC virtual impedance is constructed by controlling the grid-connected current, the frequency characteristic of the output impedance of the parallel RIC virtual impedance is remolded, the parallel RIC virtual impedance is in a low impedance state at the low-frequency harmonic frequency and the high-frequency harmonic frequency, and the harmonic suppression effect of the grid-connected inverter on the high-frequency PCC voltage harmonic is enhanced while the harmonic suppression stability is ensured. The method is applied to the grid-connected inverter, the grid-connected inverter can have both harmonic suppression stability and broadband harmonic suppression capability, and the harmonic suppression capability and the PCC power quality of the grid-connected inverter are effectively improved.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that features described in different dependent claims and herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.
Claims (6)
1. A public coupling point harmonic suppression method based on a grid-connected inverter is characterized by comprising the following steps:
s1, collecting the current of the power gridi g (n) And PCC voltagev pcc (n) At grid currenti g (n) Extracting harmonic component of current in PCC voltagev pcc (n) Extracting voltage harmonic component, and obtaining total harmonic power of the power grid in the current period according to the voltage harmonic component and the power grid current harmonic componentP t (n)，nRepresenting the current cycle;
s2, converting the total harmonic power of the power grid in the current periodP t (n) The total harmonic power of the power grid in the last periodP t (n-1) subtracting to obtain the total harmonic power difference value delta of the power gridP t (n) The virtual impedance parameter of the current cycleK v (n) And the virtual impedance parameter of the previous periodK v (n-1) subtracting to obtain a virtual impedance difference ΔK v (n) (ii) a Virtual impedance parameterK v Can be a dummy resistorR v Virtual capacitorC v Or virtual inductanceL v ；
S3, determining the virtual impedance parameter of the next periodK v (n+1)：
If ΔP t (n) Equals to 0, let the next cycle virtual impedance parameterK v (n+1) is equal to the virtual impedance parameter of the current cycleK v (n) Go to S4;
if ΔP t (n) Less than 0, judging ΔK v (n) If it is greater than 0, making the virtual impedance parameter of next periodK v (n+1) is equal to the virtual impedance parameter of the current cycleK v (n) HarmonySection factorBGo to S4; if not, the virtual impedance parameter of the next period is madeK v (n+1) is equal to the virtual impedance parameter of the current cycleK v (n) And regulatory factorBGo to S4;
if ΔP t (n) If it is greater than 0, determine ΔK v (n) If it is greater than 0, making the virtual impedance parameter of next periodK v (n+1) is equal to the virtual impedance parameter of the current cycleK v (n) And regulatory factorBAnd (3) going to S4; if not, the virtual impedance parameter of the next period is madeK v (n+1) is equal to the virtual impedance parameter of the current cycleK v (n) And regulating factorBGo to S4;
regulating factorB：
Wherein the content of the first and second substances,drepresents an adaptive coefficient;
s4, according to the next period virtual impedance parameterK v (n+1) determining the virtual impedanceZ v According to a virtual impedanceZ v And carrying out common coupling point harmonic suppression.
2. The grid-connected inverter-based pcc harmonic suppression method according to claim 1, wherein in S4, the virtual impedanceZ v Comprises the following steps:
wherein the content of the first and second substances,sis the laplacian operator.
3. The grid-connected inverter-based pcc harmonic suppression method according to claim 2, wherein the virtual impedance parameterK v As virtual electricityResistance deviceR v Said S4 includes:
s41, determining virtual impedanceZ v ；
S42 sampling PCC voltagev pcc And grid-connected current of grid-connected inverteri 2 Extracting PCC voltagev pcc Fundamental component ofv base And harmonic componentsv harm (ii) a Fundamental componentv base Obtaining the synchronous angle of the power grid through a phase-locked loopθ；
S43, synchronizing angles by using power gridθFor fundamental componentv base D-axis component obtained after park transformationv d And q-axis componentv q Sending the reference value of power current to a calculation module, and calculating the power according to the active instructionP * And reactive command powerQ * D-axis component of power current reference value is obtained through calculationi brefd And q-axis component of power current reference valuei brefq ；
S44, according to harmonic componentv harm And a virtual impedanceZ v Obtaining a reference value of the impedance remodeling currenti href ：
Synchronizing angles using a power gridθReshaping impedance to a current reference valuei href Performing park transformation to obtain d-axis component of impedance remodeling current reference valuei hrefd And impedance reshape current reference q-axis componenti hrefq ；
S45, reshaping the impedance into a d-axis component of the current reference valuei hrefd And d-axis component of power current reference valuei brefd Adding to obtain a grid-connected current d-axis reference valuei dref The impedance is reshaped to the q-axis component of the current reference valuei hrefq And q-axis component of power current reference valuei brefq Adding to obtain a grid-connected current q-axis reference valuei qref ；
S46, merging the grid currenti 2 Performing park transformation to obtain a grid-connected current d-axis componenti d And grid-connected current q-axis componenti q And respectively connected with the d-axis reference value of the grid-connected currenti dref And grid-connected current q-axis reference valuei qref Comparing, and sending the error amount to a current tracker;
s47, obtaining three-phase modulation quantity after current decoupling of output of the current trackermFor three-phase modulationmAnd performing PWM modulation, generating a driving signal for controlling a switching tube of the grid-connected inverter, and sending the driving signal to the grid-connected inverter.
4. The grid-connected inverter-based pcc harmonic suppression method according to claim 3, wherein the virtual inductorL v And selecting according to the low harmonic content of the actual PCC voltage harmonic.
5. The grid-connected inverter-based pcc harmonic suppression method according to claim 3, wherein the virtual capacitorC v And selecting according to the actual PCC voltage harmonic higher harmonic content.
6. The grid-connected inverter based pcc harmonic suppression method according to claim 1, wherein the S1 includes:
s11 sampling PCC voltagev pcc (n) And the current of the power gridi g (n)；
S12, extracting the product to be inhibitedhsub-PCC voltage harmonic componentv pcch (n) Andhsub-grid current harmonic componenti h (n) CalculatinghSub-grid harmonic powerP h (n) And total harmonic power of power gridP t (n)：
In the formula (I), the compound is shown in the specification,hrepresentative instituteThe frequency of the voltage harmonics needs to be suppressed,Nrepresenting the maximum frequency of the desired suppression voltage harmonics,
representing the PCC voltagehSub-harmonic componentv pcch (n) In the form of a plurality of such compounds,
representing the grid currenthSub-harmonic componenti h (n) In the form of a plurality of such compounds,
representing the real component of the product.
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107134798A (en) * | 2017-04-28 | 2017-09-05 | 华中科技大学 | PCC Voltage unbalances and harmonic suppressing method based on parallel virtual impedance |
| CN108258735A (en) * | 2018-03-21 | 2018-07-06 | 广东电网有限责任公司电力科学研究院 | A kind of simulation control method and system that virtual impedance is introduced in virtual synchronous machine |
| CN108429281A (en) * | 2018-03-15 | 2018-08-21 | 上海电力学院 | A kind of LCL type gird-connected inverter parallel virtual impedance adjustment |
| CN108879781A (en) * | 2018-08-01 | 2018-11-23 | 重庆大学 | A kind of grid-connected current control method based on virtual impedance correction method |
| CN109038581A (en) * | 2018-08-01 | 2018-12-18 | 湖南大学 | A kind of impedance remodeling type method for inhibiting harmonic current of VSG |
| CN109698502A (en) * | 2018-12-26 | 2019-04-30 | 电子科技大学 | A kind of multi-inverter micro-capacitance sensor harmonic resonance suppressing method of adaptive virtual impedance remodeling |
| CN111416393A (en) * | 2020-04-15 | 2020-07-14 | 上海电力大学 | Virtual synchronous generator fault current suppression method based on self-adaptive virtual impedance |
| CN111769592A (en) * | 2020-05-26 | 2020-10-13 | 国网江苏省电力有限公司盐城供电分公司 | Virtual harmonic resistance control method of grid-connected inverter based on parabola method |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105932678B (en) * | 2016-06-07 | 2018-07-06 | 湖南大学 | A kind of virtual impedance integrated control method of eletric power induction filtering system |
-
2022
- 2022-06-15 CN CN202210671561.9A patent/CN114759562B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107134798A (en) * | 2017-04-28 | 2017-09-05 | 华中科技大学 | PCC Voltage unbalances and harmonic suppressing method based on parallel virtual impedance |
| CN108429281A (en) * | 2018-03-15 | 2018-08-21 | 上海电力学院 | A kind of LCL type gird-connected inverter parallel virtual impedance adjustment |
| CN108258735A (en) * | 2018-03-21 | 2018-07-06 | 广东电网有限责任公司电力科学研究院 | A kind of simulation control method and system that virtual impedance is introduced in virtual synchronous machine |
| CN108879781A (en) * | 2018-08-01 | 2018-11-23 | 重庆大学 | A kind of grid-connected current control method based on virtual impedance correction method |
| CN109038581A (en) * | 2018-08-01 | 2018-12-18 | 湖南大学 | A kind of impedance remodeling type method for inhibiting harmonic current of VSG |
| CN109698502A (en) * | 2018-12-26 | 2019-04-30 | 电子科技大学 | A kind of multi-inverter micro-capacitance sensor harmonic resonance suppressing method of adaptive virtual impedance remodeling |
| CN111416393A (en) * | 2020-04-15 | 2020-07-14 | 上海电力大学 | Virtual synchronous generator fault current suppression method based on self-adaptive virtual impedance |
| CN111769592A (en) * | 2020-05-26 | 2020-10-13 | 国网江苏省电力有限公司盐城供电分公司 | Virtual harmonic resistance control method of grid-connected inverter based on parabola method |
Non-Patent Citations (4)
| Title |
|---|
| Analysis of Synchronous Frequency Resonance in VSG Based on the Sequence Impedance Models;Yanxue Yu等;《2019 22nd International Conference on Electrical Machines and Systems (ICEMS)》;20191205;全文 * |
| 基于自适应虚拟电阻的低压微电网多阻性逆变器下垂控制策略;康英伟等;《科学技术与工程》;20170430;全文 * |
| 基于自适应虚拟阻抗的DC-DC变换器均流控制;钱学伟等;《安徽大学学报（自然科学版）》;20160731;全文 * |
| 考虑自适应虚拟阻抗的微电网分布式功率控制策略;郭倩等;《电力系统自动化》;20161010;全文 * |
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